Domain-wall motion and interfacial Dzyaloshinskii-Moriya interactions in Pt/Co/Ir(tIr)/Ta multilayers

Kowsar Shahbazi, Joo-Von Kim, Hans T. Nembach, Justin M. Shaw, Andreas Bischof, Marta D. Rossell, Vincent Jeudy, Thomas A. Moore, Christopher H. Marrows

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57 Citations (SciVal)

Abstract

The interfacial Dzyaloshinskii-Moriya interaction (DMI) is important for chiral domain walls (DWs) and for stabilizing magnetic skyrmions. We study the effects of introducing increasing thicknesses of Ir, from zero to 2 nm, into a Pt/Co/Ta multilayer between the Co and Ta layers. There is a marked increase in magnetic moment, due to the suppression of the dead layer at the interface with Ta, but the perpendicular anisotropy is hardly affected. All samples show a universal scaling of the field-driven DW velocity across the creep and depinning regimes. Asymmetric bubble expansion shows that DWs in all of the samples have the left-handed Néel form. The value of in-plane magnetic field at which the creep velocity shows a minimum drops markedly on the introduction of Ir, as does the frequency shift of the Stokes and anti-Stokes peaks in Brillouin light scattering (BLS) measurements. Despite this qualitative similarity, there are quantitative differences in the DMI strength given by the two measurements, with BLS often returning higher values. Many features in bubble expansion velocity curves do not fit simple models commonly used, namely a lack of symmetry about the velocity minimum and no difference in velocities at high in-plane fields. These features are explained by the use of a new model in which the depinning field is allowed to vary with in-plane field in a way determined from micromagnetic simulations. This theory shows that the velocity minimum underestimates the DMI field, consistent with BLS giving higher values. Our results suggest that the DMI at an Ir/Co interface has the same sign as the DMI at a Pt/Co interface.

Original languageEnglish
Article number094409
JournalPhysical Review B : Condensed Matter and Materials Physics
Volume99
Issue number9
DOIs
Publication statusPublished - 7 Mar 2019

Bibliographical note

Funding Information:
We thank Simone Moretti and Rebeca Díaz-Pardo for their help. This work was supported by European Community under the Seventh Framework Programme–The People Programme, Multi-ITN “Wall” (Grant No. 608031), and partially supported by the DARPA Topological Excitations in Electronics (TEE) program (No. R18-687-0004). APPENDIX A:

Publisher Copyright:
© 2019 American Physical Society.

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics

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